@Puybaret
1. Your's work at new features are great and work fine.
2. I suggest few minor customization (no offense please)

In file com/eteks/sweethome3d/swing/package.properties at lines:
...
1053: HomePane.MAKE_LEVEL_VIEWABLE.Name=Make level viewable
1054: HomePane.MAKE_LEVEL_VIEWABLE.ShortDescription=Make selected level viewable

replace with:
v1
1053: HomePane.MAKE_LEVEL_VIEWABLE.Name=Make level visible
1054: HomePane.MAKE_LEVEL_VIEWABLE.ShortDescription=Make selected level visible

or bather v2
1053: HomePane.MAKE_LEVEL_VIEWABLE.Name=Show level
1054: HomePane.MAKE_LEVEL_VIEWABLE.ShortDescription=Show selected level
...
1060: HomePane.MAKE_LEVEL_UNVIEWABLE.Name=Make level unviewable
1061: HomePane.MAKE_LEVEL_UNVIEWABLE.ShortDescription=Make selected level unviewable

replace with:
v1
1060: HomePane.MAKE_LEVEL_UNVIEWABLE.Name=Make level invisible
1061: HomePane.MAKE_LEVEL_UNVIEWABLE.ShortDescription=Make selected level invisiable

or bather v2
1060: HomePane.MAKE_LEVEL_UNVIEWABLE.Name=Hide level
1061: HomePane.MAKE_LEVEL_UNVIEWABLE.ShortDescription=Hide selected level
...
1158: HomePane.DISPLAY_ALL_LEVELS.ShortDescription=Display all viewable levels in the 3D view

replace with:
1158: HomePane.DISPLAY_ALL_LEVELS.ShortDescription=Display all visible levels in the 3D view
...
1597: LevelPanel.viewableCheckBox.text=Viewable

replace with:
1597: LevelPanel.viewableCheckBox.text=Visible

I usually use the v2 for my taste.